Friday, November 30, 2012

Final look at the hurricane season

Our minds are focusing on winter weather now, and the long-range computer models still can't seem to agree on a possible change to much colder and stormier weather in mid-December, but let's take a break today and put the 2012 hurricane season to bed.

Today is the final official day of the season, and it proved to be busier than usual.

Actually, it was busy mostly for meteorologists, because the U.S. mainland -- with two notable exceptions -- escaped the wrath of the busy season.

There were 19 named storms in the Atlantic and Caribbean in 2012, and that's well above the seasonal average of 12. In fact, 2012 was tied for the fifth-busiest tropical season ever. Interestingly, that total of 19 named storms has been reached five times -- including the past three years, 2010 through 2012.

That, of course, adds support to the theory that we're in a busy cycle of tropical storm activity.

I've read the summaries on each of the 19 storms this season, and a couple things jump out at me:

THE EARLY START ... The first named system was Tropical Storm Alberto, and it formed on May 19 off the South Carolina coast.  And if that wasn't enough, Tropical Storm Beryl formed a week later, also off the S.C. coast. Both of those storms drifted southwest and made landfall in Florida.

NOTHING MAJOR ... Only one hurricane achieved "major" status, which is for Category 3, 4 or 5 storms. That was Michael, which had top winds of 115 mph as a Category 3.  Sandy and Gordon each had top winds of 110 mph. So for the most part, our busy season consisted of tropical storms and weaker hurricanes.

ONLY FOUR U.S. LANDFALLS ... And two of those were the weak early-season tropical storms, Alberto and Beryl.  The other two were hurricanes.  Isaac made landfall Aug. 28 in Louisiana, west of New Orleans. Fortunately, it caused nowhere near the damage of Hurricane Katrina in 2005. Isaac pushed northwest and died out in Oklahoma. Isaac caused $2.3 billion damage.

The other storm, of course, was Sandy. That made landfall in New Jersey on Oct. 29 and caused $50 billion damage. It has reshaped parts of the New Jersey coastline forever.  Sandy also defied logic several times, including its hard left turn into the Jersey shore. Normally, storms that ride up the East Coast generally follow the coast, rather than make 90-degree turns.

NADINE ... Few people really noticed Hurricane Nadine, and that's because it remained in the eastern and central Atlantic during its lifetime.  But Nadine was in existence, either as a tropical storm or hurricane, for 24 days. During those 3 1/2 weeks, it was carried back and forth by weak steering currents in late September.

CAROLINAS IMPACT ... Hurricane Sandy brushed the Outer Banks and did millions' of dollars in damage. However, the state was not affected by any dying tropical storms this season. Those systems often bring heavy rainfall to inland areas of the Carolinas. This year's storm tracks, however, kept weakening systems away from our region.


THAT WINTER OUTLOOK ... I plan to write again later this weekend, taking a look at that possible change in our weather pattern in two weeks or so.  The computer models keep flip-flopping on it, but it's certainly keeping meteorologists talking.

Tuesday, November 27, 2012

Winter weather postponed ... but for how long?

You might remember a week or so ago that I wrote about the computer models predicting an outbreak of very cold weather around the beginning of December.

Forget about it.

The king of weather for the eastern United States is a low pressure system off the Pacific Coast. It's called a positive East Pacific Oscillation (EPO) -- one of the many ingredients that goes into creating our weather. Here's what it means.

The positive EPO tends to send Pacific air masses into the central and eastern part of the country. For the most part, the atmospheric flow is zonal -- sort of like a flat west-to-east line.  There are some wrinkles, of course, but you get the basic idea. When that happens, our weather tends to be mild.

The pattern hasn't been exactly west-to-east in recent weeks, because a northwest flow has delivered some chilly air into the Carolinas. But the positive EPO has prevented the really cold air in Alaska from descending southward. High temperatures are below zero this week in Fairbanks.

Several factors are needed for wintry weather to develop in the Carolinas. They include a negative North Atlantic Oscillation (NAO) and possibly a strong high pressure system near Greenland.  That tends to send the really cold air into the eastern part of the United States. Add a stormy pattern, and you get snow, sleet and freezing rain.

We actually have a negative NAO now, but the positive EPO is overwhelming it -- blocking the cold air from coming south.

In addition to the positive EPO, we're also in a decidedly non-stormy pattern. Rainfall this month is more than 2 inches below average.

So how long will all this ask?

As usual, the computer models disagree.  But based on the many forecasts I've read in the last day or two, there seems a consensus that we'll stay mild through at least the first half of December.

In other words, the start of winter has been postponed.

Then again, December is typically not a big month for snow and ice in the Carolinas. That happened in 2010, but it's unusual. Most years, January and February are the real wintry months.

We need a change in the non-stormy situation.  Rainfall is badly needed, but there aren't many signs of that changing within the next 10 days either.

In the immediate future, this mild pattern means we'll be flirting with 70 degrees early next week.

CHILLY NOVEMBER: We're approaching the end of what has been a chilly month in Charlotte. The average temperature for November is 3.2 degrees below average, which makes this among the 15 coldest Novembers since records started being kept in Charlotte in the 1870s.

Sunday morning's low of 21 degrees marks the earliest it has been that cold in four years. Charlotte had a record-breaking low of 13 degrees on Nov. 22, 2008, and it dropped to 18 degrees a few days earlier. That month was 5.7 degrees below the average.

Temperatures the next few days will be around average, and it's doubtful that we'll see any more 20s in the remaining days of the month.

Friday, November 23, 2012

Wintry cold for weekend; longer- term forecast iffy

Christmas shoppers who like the idea of heading to the stores in shorts or light jackets should enjoy today. Temperatures across the Charlotte region are headed into the middle and upper 60s, after a chilly start.

But a big change is coming for the weekend, with temperatures that should please shoppers who feel they need a chill to get in the spirit.

The longer-range forecast is more uncertain, though.  Earlier this week, computer models were pointing to a dramatic cool-down and possibly even some wintry precipitation in parts of the Southeast during the first half of December.  But that looks a bit more unlikely now.

In the immediate future is an approaching cold front.

We had a chilly start Friday, and the Black Friday shoppers who visited the malls before daybreak encountered temperatures ranging from the middle 20s (26 degrees in northern Stanly County) to the mid 30s (near Charlotte).  However, temperatures soared quickly and were near 60 degrees by noon.

A rather strong cold front is crossing Tennessee at midday and should sweep across the Carolinas overnight. Fans headed out to  high school football playoff semifinals tonight should have a pleasant evening, with temperatures mostly in the 50s. The cold air won't funnel into the region until after midnight.

But you'll feel it Saturday. Highs aren't expected to climb above the upper 40s, which is below even the middle-of-winter average high temperatures. The cold temperatures will come despite full sunshine.

Sunday morning's low could be near 25 degrees, which would make it the coldest morning so far this season and the chilliest since a 24-degree low on March 6.

It will be sunny again Sunday, but still chilly. Warming begins Monday, and temperatures should remain near seasonal averages through the week.

Incidentally, Charlotte's average temperature this month also almost 3 degrees below seasonal norms -- the first time that has happened in many months.

Looking farther ahead, there are signs of a pattern change around Dec. 5-7, but it is unclear whether the atmospheric flow will be northwest-to-southeast (which would bring the cold) or more west-to-east (milder conditions).  We'll keep an eye on it next week, but as of right now, the beginning of December is looking milder than first thought.

Monday, November 19, 2012

Some talk about winter weather

I've noticed over the past few days that there is increasing talk on weather bulletin boards about the first arrival of really cold air into the Southeast.

The Global (GFS) computer model has been playing around with a scenario in which strong high pressure forms next week over southern Alaska, while a deep low pressure system develops in eastern Canada. If the two systems connect, that is the recipe for a surge of arctic air into the Southeast.

Add a low pressure system from the Gulf of Mexico, and you've got wintry precipitation in our region.

The odds favor this not happening -- not in early December.

The European model, for example, predicts the cold air will move into the Rockies. There's also a chance that the cold air remains trapped in Canada. That is the most likely scenario of the first few days of December, with Carolinas temperatures remaining around average for this time of year.

But for the first time this season, there's at least a wintry look for the eastern United States on some of the computer models.

There has been a significant change in the winter outlook across the country. Originally, meteorologists expected a weak El Nino condition, which would bring wet and chilly weather to much of the South. But now the forecast is for a neutral El Nino-La Nina situation.

That makes the North Atlantic Oscillation an important player in our weather. The NAO has been negative recently, which means weather systems have been dropping from Canada into the Southeast, then curving eastward to the Atlantic Coast, and then sweeping up the coast. That was the track of Hurricane Sandy, and it's been the same path for a couple other recent storm systems.

If that situation continues, the Carolinas will be near the "battle ground" between mild and cold air -- and in the path of storm systems. And that is a recipe for "close-call" winter storm systems, the kind that can bring sleet and freezing rain.

It's a lot of speculation now, but we should have a better idea of the pattern -- at least for early-winter -- fairly soon.

Wednesday, November 7, 2012

Warmth to return; could stay for Thanksgiving

Those of you who wish for snow and ice during the winter would love having the current weather pattern in January or February.

We've swung into a Negative NAO (North Atlantic Oscillation), which, for lack of a better description, is like an atmospheric roller-coaster. We in the Carolinas are near the bottom.

Air masses tumble southward out of Canada, curve eastward at the bottom of the roller-coaster, and then swing back to the north again, as if they're headed back up a hill. That pattern tends to bring not only cold air into the Southeast, but it also can produce a nor'easter or winter storm if low pressure gets into the atmospheric steering current.

Such a nor'easter is moving up the East Coast on Wednesday, threatening areas that were hit by Hurricane Sandy with more high water.

Temperatures in the Carolinas have been well below average recently, but the NAO is going positive soon, according to meteorologists -- before possibly going negative again after Thanksgiving.

The NAO was positive much of last winter, and the result was mild weather. Another string of mild days is likely to begin later this weekend or early next week, and it could last to Thanksgiving. Such a pattern likely would produce temperatures during Thanksgiving that are near or above-average -- similar to last year.

We might have reached the bottom of the barrel -- at least, in the current cold snap -- on Wednesday morning. The temperature fell to 29 degrees at Charlotte-Douglas International Airport, and that's the coldest since a 24-degree low March 6. If you're keeping count, that's eight months ago.

There was frost and even a freeze, which brought the growing season to an end for most people in the region.

A couple more cold nights are in store for Charlotte, with lows of 32 to 35 degrees Thursday and Friday mornings.

But then a warming trend will start. We'll see highs climb a few degrees each day, until they're near 70 degrees Sunday and Monday.

The GFS computer weather model is hinting at the development of a storm system around the middle of next week -- a warm-air system that could produce severe weather across the South.

After that, if the NAO really goes positive as it's expected to, we could continue with the mild weather for another 7-10 days, into Thanksgiving.

And then we could go back into the freezer again, if the NAO goes negative.

By the way ... some meteorologists believe we'll see plenty of NAO-negative time in the eastern United States this winter, especially after mid-January.

Monday, November 5, 2012

A gloomy Election Day (weather-wise, that is)

A developing storm system that could bring nasty weather up the East Coast -- where it is least needed -- also will deliver some rather gloomy conditions to the Charlotte region on Election Day.

It won't rain much, unfortunately, because the area is locked in a significant stretch of dry weather.

But we can expect a cloudy, chilly day. It won't be a pleasant day to be standing outdoors, should the line at your polling place be extremely long.

An upper-level low pressure system is forecast to swing southward into Alabama later Monday and then curve eastward to the Atlantic Coast on Tuesday. Once it reaches the coast, surface low pressure is predicted to form, and then ride up the East Coast.

That's right -- a nor'easter.

It's difficult to think of anything worse for people in Delaware, Maryland, New Jersey, New York and Connecticut, because of the low strengthens enough and stays close enough to shore, it could bring strong winds and heavy rain to those hurricane-ravaged areas later in the week. More about that later.

The Charlotte region will miss most of the precipitation, according to meteorologists.

Areas across southern Georgia, northern Florida and the Lowcountry of South Carolina are expected to see the rainfall from this system as it develops Tuesday. Then the precipitation, probably a steady, soaking rain, will move up across the eastern third of North Carolina.

The Charlotte area will be too far north for much rainfall, although a few showers are possible Tuesday afternoon and evening.

Charlotte won't be too far north for the clouds. High pressure over Pennsylvania will be pumping chilly air into the Carolinas, and clouds from the developing storm will add to the chilling effect.

Don't expect temperatures to climb out of the upper 40s Tuesday. The National Weather Service forecast high for Charlotte is 51 degrees, but that could be optimistic.  More likely:  Clouds and temperatures in the 40s for much of the day.

If you vote at a location where you're likely to be standing outdoor, take a warm coat and possibly a cap.

In case you hadn't noticed, our warm weather from early and mid October has sailed away. The past week has been quite chilly, and more of the same is likely for much of this work week.

Temperatures are predicted to drop into the low and mid 30s Wednesday through Saturday mornings, and areas that haven't received frost yet are likely to get some this week.

The good news is that temperatures will moderate by the weekend. Highs are expected to hit the mid 60s Friday (after mid and upper 50s Wednesday and Thursday), and we could see 70 degrees Sunday, when the Panthers face the Denver Broncos at Bank of America Stadium.

Up the East Coast: The storm will be delivering a northeast wind. That means Staten Island, lower Manhattan and Connecticut, which face south, likely won't be affected much.

But it'll be a different story for New Jersey, where Hurricane Sandy did extensive damage last week to the protective sand dunes. A northeast wind will increase the tides by a couple feet, and that could bring ocean water back into some of the cities that were hard-hit last week.